Hi, I’ve started making an 8 d.o.f biped and I have a few questions.
Thank You!
Hi,
If I understand your question, you are making a biped with 8 servos per leg. Is this correct?
I will try to answer, but others have more experience with legs with more DOF…
The voltage of the battery depends on which servos you are using. A lot of servos like the HS-422 only handle up to 6V.
I am pretty sure that the HS-422 servos will not be sufficient. They work OK for the Biped Brat, that has only 3 servos per leg and even with this, if you are going to add anything additional to the Brat, I would update to the HS-485s or better yet to the HS-645mg.
If you look at the Biped Scout with I believe 6 servos per leg and they recommend the HS-5645… My guess is that you would probably need this or more likely something like the HSR-5980… Both of these can take 7.4V
Good Luck
Kurt
Sorry, I should have been clearer. There are 8 servos in total, so 4 per leg. I’ll upgrade to the servos mentioned and see if it will work. Thank you for the help.
The additional servos are not going to require more voltage, but will require more current. That is, if you are using a battery to power your servos, it will run out of “juice” faster and you may require one rated at higher mAh. E.g. 2800mAh versus 1600mAh (See Lynxmotion - Batteries & Chargers) If you are using a wall wart, you may require one that supplies more amperage (A) at the rated voltage of your servos.
dj
The original BRAT uses 6 HS-422s and it works fairly well. Adding 2 servos is likely to require 485’s, but 645’s are better. If you have the servos, then go for it. Otherwise I would recommend upgrading.
Hi, I’m sorry but I have some more questions:
Thank You!
Yes the 5485’s would work in a 4 DOF biped. 422’s should work for arms.
Thank you!
I’m sorry but I have one last question and it is sort of unrelated to this section but since we are talking about servos I though I might as well.
I’m also making a insect/hexapod robot at the same time and I would like to ask if the HS-422 servos would be suitable for a 2 or 3 D.O.F leg?
Thank you again!
The 422’s may work for the 2DOF hexapod depending on how you do the vertical servo. If it’s done as a mechanical advantage lever like this one. It will not be a problem.
There is no hope for a 3DOF hexapod using the 422 servos.
Ok. I’m sorry but I have another question. Approximately how much torque is required for a 3 D.O.F hexapod leg? I was looking at the A-Pod that Zenta made and I think he was using
HS-645MG servos for his 3 D.O.F hexapod ant.
Thank you for the help!
Hi,
If you plan to make a hexapod equally to A-Pod size and weight, the 645’s is a minimum requirement. The 485’s might work on a Phoenix size hex but not recommended since Phoenix legs are able to stretch out pretty far meaning that the load on the femur servo gets pretty high. For saving money you can use weaker servos on the coxas, also the tibia demands less torque.
I’ve made my own brackets out of a lighter yet strong and rigid material which are similar to the lynxmotion and hitec robonova brackets to hold the motors. What is the approximate length of the A-Pod because mine will be about 30-40cm long.
Since the brackets are lighter and therefore the overall weight of the robot will be less, will I still need the HS-645 servos or will something weaker do.
Thank You for the help!
P.S. The A-Pod is soo awesome.
Thanks, glad you liked it!
A-Pod’s total length (from mandibles to tail) is about 60cm.
I would still recommend 645’s for the femurs on your hex.
Ok. Since this topic is mainly about servos now, would it be possible to change the heading to something like “Servo Information” or something.
